I was expecting to find plenty of evidence to support the American Heart Association and the American College of Cardiology. After all:
They were written by a panel of 21 scientists and health experts who reviewed more than 900 published studies.
However, the research I found went in the opposite direction. I am not convinced that it is sufficient to overturn the advice from professionals, but it would be cherry-picking not to report it here.
The most direct evidence is from the Cochrane Library which is a database of high-quality systematic reviews.
This paper looked at the effect of setting different targets in patients to lower their blood pressure. Standard targets were ≤ 140‐160/ 90‐100 mmHg. Lowered targets were ≤ 135/85 mmHg.
While setting a lowered BP target did mean that patients achieved lower BPs, it didn't improve their health on a number of factors:
Seven trials (22,089 subjects) comparing different diastolic BP targets were included. Despite a ‐4/‐3 mmHg greater achieved reduction in systolic/diastolic BP, p< 0.001, attempting to achieve "lower targets" instead of "standard targets" did not change total mortality (RR 0.92, 95% CI 0.86‐1.15), myocardial infarction (RR 0.90, 95% CI 0.74‐1.09), stroke (RR 0.99, 95% CI 0.79‐1.25) , congestive heart failure (RR 0.88, 95% CI 0.59‐1.32), major cardiovascular events (RR 0.94, 95% CI 0.83‐1.07), or end‐stage renal disease (RR 1.01, 95% CI 0.81‐1.27). The net health effect of lower targets cannot be fully assessed due to lack of information regarding all total serious adverse events and withdrawals due to adverse effects in 6 of 7 trials. A sensitivity analysis in diabetic patients and in patients with chronic renal disease also did not show a reduction in any of the mortality and morbidity outcomes with lower targets as compared to standard targets.
Looking at the confidence intervals, it is clear that it might be a little bit helpful, but the available research in 2009 wasn't enough to confirm it. (If further research has been done in the intervening 10 years, it hasn't reached the level of being reported by Cochrane.)
A related study looked at whether giving pills to people with mild hypertension (systolic blood pressure (BP) 140‐159 mmHg and/or diastolic BP 90‐99 mmHg) was worthwhile. (Note the original claim denied that this would be common, so this is a side-claim.)
- Diao D, Wright JM, Cundiff DK, Gueyffier F. Pharmacotherapy for mild hypertension. Cochrane Database of Systematic Reviews 2012, Issue 8. Art. No.: CD006742. DOI: 10.1002/14651858.CD006742.pub2.
Of 11 RCTs identified 4 were included in this review, with 8,912 participants. Treatment for 4 to 5 years with antihypertensive drugs as compared to placebo did not reduce total mortality (RR 0.85, 95% CI 0.63, 1.15). In 7,080 participants treatment with antihypertensive drugs as compared to placebo did not reduce coronary heart disease (RR 1.12, 95% CI 0.80, 1.57), stroke (RR 0.51, 95% CI 0.24, 1.08), or total cardiovascular events (RR 0.97, 95% CI 0.72, 1.32). Withdrawals due to adverse effects were increased by drug therapy (RR 4.80, 95%CI 4.14, 5.57), Absolute risk increase (ARI) 9%.
The authors called for more research to determine if the benefits outweigh the harms, but it appears in the general case, mild hypertension does not justify the use of antihypertensive drugs.
In conclusion, the Cochrane-reported research (which I generally hold in high-esteem), as of 2009, did not support telling patients to target the lower BP ranges and did not support the prescriptions of tablets for people with mild hypertension.
I would continue to recommend following your doctor's orders and/or getting a second opinion from another appropriately-trained medical professional, rather than some guy on the Internet.